In the past decade the submarine has been called upon to play an increasing role in the launching of weapon systems which break the air-sea interface. One of the present devices utilized for delivery of a weapon system to this interface is the SUBROC. This is a horizontally launched, rocket propelled missile which is exposed to the water and is controlled by a thrust vector control involving jetavators. Another device is WAM, which is a horizontally launched, rocket propelled missile which is exposed to the water and is controlled by a canard nose package. Both of these devices are denser than water and rely on the rocket propulsion to get to the surface. The rocket motor limits the depth at which the device can be launched and is a source of high amplitude noise. Both devices require active control systems which must operate in water and in air, thus requiring complex guidance hardware. Also, the missiles are exposed to water requiring them to be hardened to the hydrostatic pressure and sealed against water damage. Neither device can be simply released from the outer hull of a submarine due to the danger of igniting a rocket motor in the proximity of the submarine's pressure hull.
Another device considered for delivery of a weapons system to the air/water interface is the encapsulated POLARIS. This system is a hydrodynamically stable capsule vertically launched with a positive net buoyancy and encloses the POLARIS missile. The capsule must be launched at low speed. It has no roll stabilization, nor controls, and exits the water with a vertical attitude. This system requires a vertical tube in the submarine for its launch. When fired from the vertical tube, the water exit attitude is vertical. If fired from a horizontal tube, the water exit attitude would be a strong function of launch depth and would tend toward the vertical as the launch depth increases. The system's roll attitude at water exit would be random.